The term “expandable” is used as a defined term of art throughout this disclosure. By “expandable”, this disclosure refers to culverts and pipes that, when cut longitudinally in situ underground, may then be radially expanded, preferably nondestructively, by separation and widening of the longitudinal cut, so that the expanded pipe (or expanded “host” pipe as sometimes referred to herein) may then receive a new inner liner pipe whose internal diameter is at least the same as, if not larger than, the internal diameter of the original unrefurbished host pipe. It is expected that many culverts or pipes falling within this definition will be metal, and will be corrugated or “accordion” in profile. However, the term is not limited to corrugated or accordion profiles on metal pipes or culverts.
The Prior Application, incorporated herein by reference, discloses a trenchless technology, now patented, for nondestructively refurbishing underground pipes. Generally speaking, the Prior Application describes embodiments in which a longitudinal cut is initially made in the host pipe. In some embodiments disclosed in the Prior Application, the host pipe is then radially expanded, preferably nondestructively, by separation and widening of the longitudinal cut. A new liner pipe is then inserted into the expanded host pipe. Preferably, the internal diameter of the liner pipe is at least the same as, if not larger than, the internal diameter of the original unrefurbished host pipe. Grout may then be injected into the annular space between the liner pipe and the host pipe.
The Prior Application further describes some of the problems that its disclosed technology solves, and some of the technical advantages enabled in solving such problems. While embodiments of the Prior Application have been shown to be highly serviceable, and indeed highly advantageous, improvements have been identified in deployments where the host pipe is located, for example, under roads in mountain passes with steep inclines on one side and open waterways nearby on the other side. Such locations may often present additional access challenges in deploying the embodiments of the Prior Application. As is shown on FIG. 1, host pipe H is buried beneath road R with steep incline SI on one side and waterway W on the other side. In the exemplary environment illustrated on FIG. 1, access to host pipe H on the waterway W side is from above only. Access to host pipe H on the other side is very limited by steep incline SI. It will be appreciated that, for example, the location of host pipe H presents challenges to installing a new liner pipe inside host pipe H if the liner pipe is approximately the same length as host pipe H. There is not enough room on the steep incline SI side to insert a full-length liner into the host pipe H from the incline side, and waterway W prevents practical insertion of a full-length liner into host pipe H from the water side.
Conventional prior art solutions to the above-described access challenges present additional problems. For example, a “cured in place” or “CIPP” method is known, in which a collapsible liner, or “sock” is unrolled into host pipe H and then expanded with steam and cured onto the inside of host pipe H. Such CIPP solutions lack the structural integrity of a rigid liner pipe solution, and their robustness against cracking and leaking in service is not as good as a rigid liner pipe solution.